1. Field of the Invention
The present invention relates to a coating nozzle for applying a coating solution such as a photoresist or the like to a surface of a workpiece such as a glass substrate, a semiconductor wafer, or the like, a method of coating a workpiece with such a coating nozzle, and a coating device incorporating such a coating nozzle.
2. Description of the Relevant Art
Photoresists are coated on glass substrates for use in liquid crystal display panels to produce color filters thereon, and various coating solutions are coated on the substrate surfaces of semiconductor wafers. For uniformly coating such a solution on a substrate, it has been customary to drop the solution onto the central area of the substrate and rotate the substrate with a spinner at a high speed to spread the dropped solution uniformly over the entire surface of the substrate under centrifugal forces.
When the substrate is rotated with the spinner, however, since the dropped solution needs to be spread uniformly to the outer peripheral edge of the substrate, a large amount of solution tends to be scattered off the substrate, resulting in a large consumption of the solution before the substrate surface is fully coated with the solution.
Coating devices having a slit nozzle for minimizing the amount of a coating solution to be applied to a substrate have been proposed in the art. For example, such coating devices are disclosed in Japanese laid-open patent publications Nos. 63-156320, 4-332116, and 6-151296.
The coating devices shown in Japanese laid-open patent publications Nos. 63-156320 and 4-332116 have a slit nozzle positioned over a substrate to be coated. While the substrate is slowly rotating below the slit nozzle, a coating solution is dropped from the slit nozzle onto the upper surface of the substrate, so that the coating solution is coated to a certain uniform thickness on the upper surface of the substrate. Thereafter, the substrate is rotated at a high speed to render the coated thickness of the solution more highly uniform.
According to Japanese laid-open patent publication No. 6-151296, a coating solution is discharged under pressure from a slit nozzle while the slit nozzle is moving closely along a surface of a substrate. The coating solution discharged from the slit nozzle is pressed against the substrate surface by the tip of the slit nozzle, forming a flat solution layer on the substrate surface.
As revealed in the above publications, the amount of the coating solution used can be minimized when the substrate is rotated at a high speed after the coating solution has been applied to the substantially entire surface of the substrate through the slit nozzle.
The slit nozzles disclosed in the above publications comprise either a number of nozzle orifices arranged in line or a single thin elongate nozzle orifice for ejecting the coating solution in a slit pattern having a certain width. The disclosed slit nozzles tend to allow the coating solution to fall off as droplets and suffer localized discharge pressure variations, failing to coat the coating solution as a uniform layer.